Engineers in Microsoft's research division> have developed an automatic-identification technology known as InfraStruct, using passive tags operating in the terahertz (THz) band. Instead of encoding data onto a silicon chip, as is typically the case for passive RFID tags operating in the low-frequency (LF), high-frequency (HF) or ultrahigh-frequency (UHF) radio frequency (RF) bands, the InfraStruct system involves building a unique shape or hollowed section directly into a structure, with an ID number or other data physically represented in that shape or section.

The term terahertz refers to electromagnetic radiation falling between microwaves and infrared—that is, between 300 GHz and 3,000 GHz (0.3 THz to 3 THz), with wavelengths ranging from 0.03 millimeter to 3.0 millimeters (0.001 inch to 0.1 inch). The UHF band, meanwhile, ranges from 300 MHz to 3 GHz, with wavelengths from 10 centimeters to 1 meter (3.9 inches to 3.3 feet).

Samples of the InfraStruct tags used by the researchers during their experiments

The InfraStruct concept, still in the prototype stage only, includes a unique method of building a tag into a three-dimensional printed plastic object, as well as a terahertz scanner that transmits an optical-like radiation into the item that is reflected back to the scanner. Software then measures the response of the reflection received, thereby identifying the unique item based on that measurement.

Andrew D. Wilson

Karl D.D. Willis, formerly a research intern at Microsoft Research while a Ph.D. candidate at Carnegie Mellon University, and Andrew D. Wilson, a principal researcher at Microsoft, developed the technology throughout the past several months, hoping to enable a unique identification method as an alternative to bar codes and radio frequency identification. Bar codes, they explain, must be placed outside an item, and thus create an aesthetic problem. Adding an RFID tag (with a silicon chip and antenna) to a molded object made only of polymer, on the other hand, would disrupt the manufacturing process used to form that item.

With InfraStruct, a 3D printer could be used to create objects based on computer-controlled digital fabrication. Those items could differ slightly from one another, due to slight changes in the digital design, creating an opportunity for the unique identification of each of otherwise seemingly identical objects. Such identification can be useful during inventory tracking, logistics or gaming applications, but could be used in the future to help a robot recognize specific objects it seeks.